All complaints relating to patients treated in a 20 bed observation unit of a large teaching hospital over a 26-month period are reviewed. From May 1994 to July 1996, 11,042 patients were admitted to the observation unit. During this period there were 28 patient complaints. These complaints consisted of staff attitude/behavior (42.9%), discharge processes (25%), environmental concerns (17.9%), difficulties with diagnostic investigations (10.7%), and miscellaneous issues (3.6%). The type and frequency of complaints were similar to those received in other areas of the hospital, although the profile of complaints was different to those commonly experienced in the emergency department. Observation units are frequently considered to be an extension of the emergency department. Patient complaints received in relation to care received in an observation unit are similar in nature to those recorded in inpatient units as opposed to those received in emergency departments.